Heretofore in the operation of electric vacuum cleaners, especially where the vacuum cleaner was a small one and intended to be hand held and, therefore, operated in close quarters, a flow through motor was utilized. In such a vacuum cleaner, the flow of air is substantially axial, starting at the forward end of the motor housing, through filtering means, going past the motor and then out through a vent at the rear of the motor housing.
However, some hand held vacuum cleaners are used to pick up material which is explosive in quality. The passage of contaminated air, even after it has been filtered, past the vacuum cleaner motor may create difficulties especially where the motor produces sparks, as frequently occurs at the brush contacts of the motor.
Thus, for instance, during the vacuum cleaning of excess toner from an electrostatic reproduction apparatus, there is danger because the toner is extremely explosive. It is important that the air stream in the vacuum cleaner, which is contaminated with particulate material, not pass over or through the vacuum cleaner motor itself.